Method of providing an electrically conductive network on a support of insulating material



Feb. 24, 1959 A. J. DE ROOY ET AL 2,

METHOD OF PROVIDING AN ELECTRICALLY coNDucTIvE NETWORK ON A,SUPPORT OF INSULATING MATERIAL Filed Dec. 27, 1955 INVENTORS ANTONIUS JOHANNES DE ROOY JOHANNES JOSEPHJS ANTON IUS JONKERS AGENT 2,874,449 METHOD OF PROVIDING AN ELECTRICALLY CONDUCTIVE NETWORIQON A SUPPORT OF INSULATING MATERIAL 1 Antonius Johannes de Rooy and Johannes Jos'ephusAntonius Jonkers, Eindhoven, Netherlands,,assignors, by mesne assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware Application December 27, 1955, Serial No. 555,665

Claims priority, application Netherlands December 30, 1954 1 Claim. 01. 29-2514 which ,thecharge image is renewed after each scan. The

methd of deriving information from the charge image by means of an electron-beam without appreciablyreducing the chargeon the insulating surface as effected in electron tubes is termed memory tubes. These tubes permit light flashes or other transient, non-recurring phenomena to be studied. This also permits a bright image of articles of very low luminosity to be obtained.

Memory tubes are known which comprise a grid-shaped electrode consistingot an electrically conductive network unilaterally provided with a thin layer of insulating material, the network serving as a support'for the insulating layer.

In a further form the conductive network functions as a supportfor a layer of insulating material covering one side of the network throughout its surface and closing the openings of the network. Hence, the screen has a closed surface at one side divided into partitions by the metal network.

By collecting the electric charge the potentials of the insulating surfaces are subject to variation within the boundaries formed by the network, the surfaces becoming more'or less negative. A beam of electrons of low velocity directed to the screen experiences the influence of the potential differences, the current of electrons passing to the network being determined by the value of the potential diiferences relative to the network. The picture signal may be derived from the remaining electrons returning from the screen and also from electrons carried off by the network. Production in either manner of the picture-signal is Widely used in television pick-up tubes of the orthicon type.

Electrodes in which the conductive network functions as a support and the insulating layer is stretched in the form of a film over the network suffer from a limitation a in that the number of meshes per cm. of the network at a given ratio between the size of the openings and the metal surface is limited by the thickness of the material required to make the network sufficiently rigid.

A further limitation is that the network extends above the insulator surface. In this respect it is to be considered that when using a grid-shaped electrode placed in the path of a stream of electrons, the velocities of which are to be varied in the plane of the grid, the required potential difference between the grid and an electrode placed behind it may be smaller as the spacing between the electrode and the grid is smaller. In the conventional construction the distance within which the potential fields influencing the electron velocity are active depends upon the thickness of" the material, since the equipotential surface of the grid extends between the highest 5 United States Patent O aforesaid disadvantages.

peaks of the network extending above the insulatorsurface. This is prohibitive to minimizing the potentials for charging the insulator-surface, which is desirable since the surface-conduction of the insulator increases with the value of the potential difference relative to the grid, so that greater potential differences promote the leakage of the image charge.

The present invention has for its object to mitigate the It concerns a method of .making an electrode consisting of the combination of an insulator and a metal network, the insulator constituting the support and the network being provided in the form of an exceedingly thin metal deposit on the surface of the support. 1

The invention yields a print of a grid produced according to a conventional technique and known as a commercial product. In the first phase of the method in accordance with the invention the grid is provided on the insulator. As the insulating material mica is preferably used, but glass and oxidized aluminum are also suitable.

In order to be a satisfactory insulator the aluminum should be thoroughly oxidized.

Subsequently a thin layer of material is spread over the insulator-surface carrying the grid, said material consisting of a soluble fine-crystalline material. A suitable material is barium chloride for which water may be used as a solvent. The grain size of the material is preferably chosen to be smallerthan 1 micron. A suitable layer is obtained by applying the material by vaporisation.

The grid is coated with it and the material deposits through openings of the grid onto the insulating surface.

cally conductive.

Subsequently, the grid is carefully removed and the material applied by vaporisation remains in the openings on the insulating surface. This surface then exhibits blocks of the material,f applied by vaporisation, sura reticulate pattern.

After that, a thin metal layer is provided by cathode disintegration throughout the surface. It is required therefore that the metals used are capable of being pro .vided in the form of such a thin layer that the material applied by vaporisation dissolves through the metal layer. However, the metal layer should be sufficiently electri- The metal must not be attacked by the solvent and should firmly adhere to the surface of the insulator. Suitable metals are gold, silver, platinum, palladium and iridium.

During the next step of the manufacturing method the material applied by vapori'sation is dissolved in a suitable liquid. For this purpose the insulating plate may be immersed in the solvent. Where the metal does not directly contact the insulating layer it does not adhere to the surface of the insulator after the intermediate layer is dissolved.

Finally the solvent is removed and the surface is cleaned. To this end damp wadding is cautiously swept over the surface, thus removing any superfluous metal i. e. metal particles unable to adhere to the surface because the intermediate layer is carried oif together with the solvent thus leaving nothing for the metal that had been on the surface of the intermediate layer to adhere In order that the invention may be readily carried into effect it will now be'described with reference to the accompanying drawing, given by way of example, in which the diiferent phases of the method are shown in Figs. 1 to 6.

. Fig. 1 shows an insulator-plate 1 carrying a grid 2 which should extend fiat throughout the surface of the plate 1. This is achieved by using an electro-static field. For this purpose the plate is placed on an electrically Patented Feb. 24,1959

conductive support and 'to thegrid 2 an electric-potential .is applied by means of .a supply 4.

Fig. 2 is a cross-section after covering the grid 2 and the insulator-plate 1 with a layer of fine-crystalline material. Besides barium chloride, calcium fluoride or an alkaline earth halide, which are also soluble in water, may be used for said material;

The wires of the grid 2 have a circular or substantially circular cross-section so that their surface contactingthe support 1 is smaller than, their thickness. By a judicious manner of applying the crystalline material by vaporisation the result is obtained that the .uncovered areas on the surface of theinsulator are minimized. To

this end the vaporisers 7 are arranged laterally and directed to the surface at different angles. This .requires the use of four vaporisers, two of which are arranged in the plane of the drawing.

Fig. 3 shows a cross-section after removal. of. the

grid 2. The size of the covered fields in proportion to the total surface is more favourable than when applying the material by vaporisation from a direction at right angles to the insulator, thus producing a better opening ratio.

Subsequently the layer 6 of conductive material is pro-.

vided (Fig. 4). a

Fig. 5 shows the condition in which the material 5 applied by vaporisation has been removed so that the metal layer 6 is connected only by narrow strips to the surface Y the invention may be extended to a method of manul l i i degree o'faccuracyj The method in accordance with facturing such grids. To this end the insulator-plate together with the network formed thereon is immersed in an electrolytic copperbath, in which the conductive network is provided with a copper layer. The cQPPer layer is allowed to .grow to thickness thus comprising sufiicient rigidity on the grids. Subsequently the thickened'layer of copper is taken from the insulator, the

initial conductive network .left beingused for manufacturing'the next grid. a I

'What'is claimed is: A method of forming a copper metal grid comprising the steps, placing a finely-meshed metal grid on the surface of an insulating support, coating said surface and metal grid with a thin layer of a finely-divided soluble crystalline material, removing the grid thereby removing the crystalline material. that had been on the grid surfaceand exposing portions of the insulating support surface corresponding to the grid, coating the layer of.

crystalline material and exposed surface of the insulating support with a thin layer of metal, immersing the insulating support in a solvent for said crystalline ma-' terial until the solvent has penetrated through the metal layerand has dissolved the crystalline material, removing the dissolved crystalline material and metal not adhering directly to the surface of the insulating support thereby forming a metal print of said network on the --insu'lating support, electrodepositing on said metal print a layer of copper of sufiicient thickness to form a rigid copper grid and removing the thus formed copper grid from the insulating support.

References Cited in the file of this patent UNITED. STATES PATENTS 2,047,369 Hickock July 14, 1936 2,160,510 Moller May 30, 1939 2,618,762 Snyder Nov. 18, 1952 2,644,208 Auphan July 7, 1953 2,706,264 Anderson Apr. 12, 1 955 

1. A METHOD OF FORMING A COPPER METAL GRID COMPRISING THE STEPS, PLACING A FINELY-MESHED METAL GRID ON THE SURFACE OF AN INSULATING SUPPORT, COATING SAID SURFACE AND METAL GRID WITH A THIN LAYER OF A FINELY-DIVIDED SOLUBLE CRYSTALLINE MATERIAL, REMOVING THE GRID THEREBY REMOVING THE CRYSTALLINE MATERIAL THAT HAD BEEN ON THE GRID SURFACE AND EXPOSING PORTIONS OF ATHE INSULATING SUPPORT SURFACE CORRESPONDING TO THE GRID, COATING THE LAYER OF CRYSTALLINE MATERIAL AND EXPOSED SURFACE OF THE INSULATING SUPPORT WITH A THIN LAYER OF METAL, IMMERSING THE INSULATING SUPPORT IN A SOLVENT FOR SAID CRYSTALLINE MATERIAL UNTIL THE SOLVENT HAS PENETRATED THROUGH THE METAL LAYER AND HAS DISSOLVED THE CRYSTALLINE MATERIAL, REMOVING THE DISSOLVED CRYSTALLINE MATERIAL AND METAL NOT ADHERING DIRECTLY TO THE SURFACE OF THE INSULATING SUPPORT THEREBY FORMING A METAL PRINT OF SAID NETWORK ON THE INSULATING SUPPORT, ELECTRODEPOSITING ON SIAD NETWORK ON THE COPPER GRID AND REMOVING THE THUS FORMED COPPER GRID FROM THE INSULATING SUPPORT. 